1. Field of the Invention
The present invention relates generally to communications networking, and more specifically, to classifying signals transported over a communications network.
2. Related Art
Architects of communications networks continuously seek to achieve an optimal balance among various network characteristics. Such characteristics include bandwidth demand and quality of service parameters, such as latency, loss, or priority. For example, data-over-cable networks are expanding the variety of services traditionally provided to subscribers. In addition to television broadcasts, cable providers are offering telephony, messaging, and Internet services. As a result, additional bandwidth is needed to support the timely delivery of these services. Moreover, traditional cable broadcasts primarily require one-way communication from a cable service provider to a subscriber's home. As interactive or personal television services and other nontraditional cable services continue to be offered, communications media used to support one-way communications must now contend with an increased demand for bi-directional communications.
In a conventional cable television communications network, a communications device (such as a modem) requests bandwidth from a headend device prior to transmitting data to its destination. The headend device allocates bandwidth to the communications device based on availability and the competing demands from other communications devices. Typically, bandwidth is available to transmit signals downstream to the communications device. However in the upstream, bandwidth is more limited and must be arbitrated among the competing communications devices.
Depending on the type of service being hosted by the communications device, some communication devices or their services are granted higher priority over others. For example, telephony is less tolerant of latency, jitter, and loss than a data messaging service. As such when a voice packet arrives at the headend device, the voice packet is processed before any data packets are processed. This priority processing is implemented by application software linked to the data link layer within the headend device. At the physical layer, an electrical signal carrying a voice packet is not conventionally distinguished from a signal carrying data.
Accordingly when a signal is received at the physical interface of a headend device, the signal is delivered to the data link layer for further processing. All signals are treated alike at the physical interface, without regard to priority or other quality of service parameters. As a result, signals are forwarded to the data link layer on a first-come-first-served basis. Some of these signals may contain a higher priority packet (such as voice) requiring expedited handling to ensure good application performance. Others may contain a lower priority packet from a service that is more tolerant of delays while still providing acceptable performance standards.
Upon receipt of the signal by the data link layer, application software classifies the signal into two or more levels of priority but only after protocol processing has been completed. As a result, a signal containing a lower priority signal could be forwarded to the data link layer for protocol processing before a signal from a higher priority service. The delay resulting from forwarding a lower priority signal to the application software before forwarding a higher priority signal could be harmful to performance of the associated higher priority service. For instance, this conventional method can introduce approximately fifty to a hundred milliseconds of delay. Although it may be tolerated by data services, this amount of delay can be problematic to voice scheduling.
Therefore, a packet prioritization method and system are needed to address the above problems.